Some properties of the KS potential, concerning degenerate and nearly degenerate states

We show that the KS potential of a degenerate state depends only on its sym metric part. The nonsymmetric part has to be abandoned both from the Hartre e as well as from the exchange and correlation potential. The same picture prevails when a perturbation breaks the symmetry, i.e. the perturbation KS potential must have the same transformation properties as the external pote ntial and must tend to zero when the external perturbation tends to zero. ( C) 2000 Elsevier Science B.V. All rights reserved.